EA028187B1 - Combustion process for fuel containing vanadium compounds - Google Patents

Abstract

Oxycombustion process wherein low ranking, gaseous, liquid, solid, optionally solid melting hydrocarbon fractions are used as fuels, having a vanadium content in an amount by weight from 50 to 500 ppm or higher, for producing energy, wherein magnesium is added as oxide, or as a water-soluble salt, the combustor being refractored and isotherm or quasi isotherm, flameless, working at temperatures comprised between 1,250 and 1,450°C and under pressurized conditions, wherein the oxidant is oxygen, the oxidant being used in admixture with water or steam, the ratio by moles oxidant:(water-steam) is comprised between about 1:0,4 and about 1:3 or the oxidant is used in admixture with flue gases recycled from the flue gases outletting the energy recovery equipments, wherein the water amount is higher than 30% by volume, optionally by adding water, the molar ratio oxidant:(water/steam) in flue gases being comprised from about 1:0.4 to about 1:3; the low ranking hydrocarbon fraction containing vanadium is fed in admixture with water or steam in the amount of water/steam being at least 30% by weight with respect to the hydrocarbon fraction.

Description

The present invention relates to a method for burning low-quality fuels with a vanadium content of from 50 to 5,000 rpm to produce flue or flue gases containing a low amount of fly ash on a dry flue gas mass, <10 mg / m ³ , preferably <5 mg / m ³ per dry weight, insignificant amount of non-combustible residues, where the weight amount of total organic carbon (OOC) is <1 ppm, PAHs (polyaromatic hydrocarbons, mainly pyrenes) <10 ^-4 mg / m ³ , in the absence of soot, the amount of vanadium or its compounds is lower , than 1 mg / m ³ , and in the form of ν2Ο5 in an amount of <0.01 mg / m ³ and not detectable by X-ray analysis (XRD) Νανθ3. In addition, these flue gases do not affect the building material of the combustion chamber and energy-using devices and do not cause a decrease in efficiency due to pollution by sticky deposits of devices used for energy consumption.

More preferably, the present invention relates to the use of low-quality hydrocarbon fractions for energy production, such as, for example, petrolenes and asphaltenes containing large amounts of vanadium, in combustion chambers operating at temperatures in the range 12501450 ° C, combustion chambers that are part of energy-using plants and operating 8,000 h / year or more non-stop to clean equipment or to replace corroded or irreparably damaged parts with sintered powders deposited by flue gases Without deteriorating efficiency and lowering energy; essentially, in residual powders, astringent compounds, in particular sulfates and soot, are practically absent or are in negligible amounts.

It is well known from the prior art that as a result of refining various types of crude oils in order to obtain industrial hydrocarbon fractions, such as fuel, petrochemical products, fuel for energy production, heavy hydrocarbon fractions, in particular petrolenes and asphaltenes, are formed as by-products. These by-products cannot be directly used for the production of industrial hydrocarbon fractions and find more limited use, for example, as road asphalt or specific fuels such as fuel oil, bitumen pitch, residues after light cracking or secondary distillation of oil, suitable for energy production, but only using sophisticated complete energy conversion plants to avoid the negative technological and environmental effects that would occur if Using conventional hydrocarbon plants or factories. In fact, carbon compounds, polyaromatic hydrocarbons, for example, asphaltenes, highly molecular linear or branched hydrocarbons, for example, petrolenes, compounds having chemical structures more difficult to undergo complete combustion are concentrated in heavy hydrocarbon fractions. For example, more sophisticated plants should be used for fuel oil, such as those used for coal, which include a large number of sophisticated equipment, especially in the after-treatment section of flue or flue gas. In fact, this causes a decrease in the industrial value of fuel, in addition to creating problems in terms of operating costs and environmental impact on the environment.

Another way of using the aforementioned heavy fractions as fuel is to convert them, for example by gasification, followed by complex gas cleaning processes, in order to use gas obtained in conventional combustion chambers, for example a combined gas turbine cycle, to generate energy. In addition, heavy fractions are subjected to complex catalytic reforming processes to obtain commercially valuable higher hydrocarbon fractions.

However, these processes require substantial investment and costs and specialized enterprises. Of course, the decrease in the industrial value of these fuels is still preserved due to the accumulation and concentration in these fractions of certain products, for example, sulfur and nitrogen, remaining after hydrogenation processes at refineries, and chemically bonded high molecular weight compounds present in crude oil, which are preferably concentrated in heavy hydrocarbon fractions. Fireproof slags and some heavy metals, in particular vanadium and nickel, behave similarly.

It is known that vanadium is a part of porphyrins, typical products of the orogenesis of fossil hydrocarbons, and is present in various types of crude oils, mainly in an amount proportional to the content of polyaromatic hydrocarbons. In oil refining processes, bound vanadium is concentrated in heavy hydrocarbon fractions. Removing vanadium of course reduces the problems in obtaining valuable commercial fractions, but on the contrary increases the problems associated with the use of heavy hydrocarbon fractions. For example, conventional oil having a density of 105-110 ΑΡΙ may contain vanadium in very different quantities, depending on the production wells, generally of the order of 50-100 ppm. However, in the heavy fractions obtained from this crude oil, the concentration of vanadium may increase to 200-300 ppm. When a heavy fraction or heavy oil undergoes a process of separating asphaltenes, in order to obtain an upgraded oil

- 1 028187 of higher quality, the vanadium content in these fractions increases. For example, in the asphaltene fraction, the concentration of vanadium may increase to 500-700 ppm.

It is also known that in the residues from the processes of catalytic conversion / gasification / reforming of heavy hydrocarbon fractions, the content of vanadium can reach several thousand ppm.

It is also known that vanadium is a significant problem for human health and environmental impact, as well as a technological problem in industrial plants in terms of its aggressiveness in relation to various materials used, such as heat-insulating refractory materials, steels, high-quality alloys (alloy steels).

Various methods are known from the prior art for reducing the negative effects of vanadium in plants for converting fuel into energy. See, for example, I8 patent 2843200 for a method for reducing the corrosive effect of vanadium-containing fractions by introducing an inhibitor, which is finely atomized calcium hydrosilicate, into the combustion chamber, or by uniformly mixing the inhibitor with fuel. The description of this patent indicates that fly ash resulting from the combustion of residual fuel oil containing significant amounts of vanadium compounds has a significant corrosive effect on building materials of energy-consuming plants, for example, catastrophic oxidation of turbine blades is observed. The effect of corrosion is believed to be due to the presence of ν ₂ Ο ₅ , which is formed during the combustion of residual fuel oil containing vanadium. This compound aggressively affects various metals, their alloys and other building materials. The corrosive effect progressively increases with the temperature of the flue gases. In addition, vanadium ash containing flue gases forms a solid and sticky material that causes corrosion and deposits on the equipment walls and thickens them. When using the additive described in this patent, the vanadium-containing fly ash does not adhere to the metal parts of the equipment, but settles in the form of non-adherent, easily removable powders. However, it is noted that the corrosive effect on various equipment materials is maintained, but only delayed. This patent proposes to carry out the process in the combustion chamber at relatively low operating temperatures, not more than 750 ° C (for example, 1350 ° P, 732 ° C). One of the drawbacks of this process is that fly ash contains a high amount of combustion residues, which subsequently pollute the equipment with deposits. Patent I8 2781005 describes the use of inhibiting additives based on magnesium and zinc in the form of oxides or in the form of compounds from which their oxides are formed when the temperature is maintained in the combustion chamber, when working with vanadium-containing low-grade residual fuel oil. The effect of the temperature of combustion of flue gases in the range of 600-800 ° C on energy-using devices, such as turbine blades, is also described. The example given in the patent describes the process at 650 ° C. Additives are supplied to the combustion chamber optionally mixed with fuel. In this case, corrosion is observed at the same level as in the absence of vanadium. Compositions containing zinc and magnesium oxides lead to the formation of тов ₃ ν ₂ Ο ₈ orthovanadates with the simultaneous disappearance of ν ₂ Ο ₅ from flue gases. The patent states that when the added amount of the additive is lower than indicated, the corrosion does not significantly decrease, probably due to the presence of free ν ₂ Ο ₅ in the flue gases. The disadvantages of the additives used in this patent are the same as the previous patent. Patent I8 3817722 describes the reduction of both corrosion and pollution from fly ash adhering to the walls of equipment during the combustion of fossil fuels containing vanadium and alkali metals by adding compounds that form silicon and magnesium oxides as sources of silicon and magnesium, so as to provide a weight ratio of 8ίΟ ₂ / Μ§Ο higher than 2: 1, preferably higher than 3: 1. At least two parts by weight of magnesium / one part by weight of vanadium and at least two parts by weight of silicon / one part by weight of alkali metals must be present. The higher the ratio 8ίΟ ₂ / Μ§Μ, the higher the inhibition of corrosion and the formation of deposits of fly ash. With a high sodium content, the ratio of 8ίΟ ₂ / Μ§Ο can reach 6: 1. The patent states that cheap fuels, which are fuels containing vanadium and optionally also alkali metals and sulfur compounds, are difficult to process. It is indicated that it is known in the art to use silica to control volatile tar deposits on energy-using equipment.

Other prior art patents describe the use of Μ§Ο and 8ίΟ ₂ in a ratio of 1/1 to 2/1. However, as is known from the prior art, if a combustion temperature higher than 760 ° C. is used, corrosion and deposition of fly ash occur. Therefore, additives effective at these temperatures are not effective at temperatures higher than 760 ° C due to the melting of fly ash followed by corrosion and contamination. It was shown that 8ίΟ ₂ is effective in modifying the properties of volatile resin Pollution Prevention energy using equipment and corrosion inhibition. In this method, the melting temperature of the ash is increased so that the presence of a corrosive liquid phase is eliminated. However, this is true for temperatures up to 700 ° C. At temperatures in the range of 815-870 ° C, corrosion and fly ash pollution will again occur. In other words, the use of the prior art additives is highly ineffective in the case of an inexpensive vanadium-containing low-grade fuel at combustion temperatures above

- 2 028187

800 ° C.

Systems for achieving temperatures above 760 ° C are based on pre-treatment of fuel by washing with water to remove alkali metals and the subsequent addition of magnesium sulfate in a weight ratio of MD / ν = 3/1. The disadvantage of this treatment is that a significant contamination of the turbine blades of energy-using devices occurs with a progressive decrease in energy production. In practice, the magnesium / vanadium ratio can at best be 3 / 1-3.5 / 1 for a good balance between corrosion protection and minimal energy loss. However, turbine operation must be interrupted to clean the blades by rinsing. In fact, one part of the modified ash is deposited on the blades of the turbine, the operation of which should be stopped and subjected to washing with water. These cleaning operations require approximately 6 hours, therefore such treatments can only be carried out on turbines that can be intermittently stopped. They also tried to wash them using chopped nutshells in order to speed up the process, however, small advantages were achieved. In the prior art, equipment made of alloy steel, in particular alloys containing nickel and cobalt, was used to improve corrosion resistance. However, an obvious improvement at temperatures of 400-500 ° C was not achieved at temperatures above 700 ° C. Thus, the equipment has a significantly lower period of operation compared to the case when using vanadium-free fuel. As shown in the examples cited in the patent υδ 3817722 (see above), the examples described in this document, the additive allows burning at temperatures up to about 815 ° C. The disadvantage of this additive is the high ratio δίΟ ₂ / Μ§Μ, at least 6: 1, necessary in order to achieve a reduction in corrosion. Another disadvantage is that the corrosion process is reduced, but not completely eliminated. To avoid corrosion from the melting of the ash, the temperature should not exceed 815 ° C. In addition, in the presence of sulfur, Μ§δΟ ₄ is formed, which excludes magnesium from these reactions. Magnesium sulfate is an adhesive adhesive to the walls of energy-using equipment and thus reduces the efficiency of energy production. Magnesium is also used in the case of gasification of fuels to produce synthesis gas, which is used in steam boilers or in combined cycles, achieving the same effects as in the aforementioned prior art in direct combustion chambers, using low-quality fuel to produce hot flue gases. However, in these cases, before using the synthesis gas in the thermodynamic cycle, it is necessary to ensure the removal of the powder formed by hard to remove solid streams (vanadium sludge), and to carry out further complex actions to remove residual vanadium present in the form of ultrafine particles.

From the prior art it is known, see the article by E. Kossa s1 a1., No.ske1 Οχίάβ aΝ Νρ »ΙηЫЬог о £ Vаηаά ^ it- ^ ηάiseά But! Soggokuyp δiρе ^ а11о8-Sotρa ^^ 8оη Ю ΜΟΟ-όαδοп 1пЬЬьог, 1. Ма1. Svet., 2002, 12, 3766-3772, that the use of fuels containing vanadium and sodium causes the accumulation of ash along the path of the flue gas. This ash causes pollution and corrosion along the gas path as a result of the formation of chemically active compounds having a low melting point. The additive used in this publication is formed from ΝίΟ-Μ§Ο used at temperatures up to 850-1000 ° С. The formation of nickel orthovanadate significantly reduces corrosion and ash deposition. The action of Μ§Ο on the ash stabilizes vanadium in the form of mixed sodium magnesium orthovanadate ΝαΜβ, / νΟ, ιΚ However, the conversion of Μ§Ο to sulfate due to the presence of sulfur in the fuel provides, for the formation of mixed orthovanadate, the supply of excess magnesium sulfate to the fuel, adhesion which is known. As a result, dense deposits form on the walls of the equipment, which creates known inconveniences. The publication concludes that ΝίΟ is an effective alternative to Μ§Ο with respect to vanadium-induced corrosion. It is emphasized that chromium oxide and alumina form the corresponding orotvanadates. However, these compounds in the molten state also cause corrosion, and the higher the amount of sodium, the higher the corrosion. The addition of Μ§Ο as an inhibitor leads to the formation of mixed orthovanadate, which in turn leads to a decrease in corrosion, but due to the excess magnesium / vanadium ratio, the amount of ash increases, which is also an adhesive. The publication states that, unlike magnesium orthovanadate, nickel orthovanadate is insensitive to the presence of sodium. Mixed sodium and magnesium vanadates ΝαΜ§ ₄ (νΟ ₄ ) ₃ , even though they are refractory and inert compounds, are low melting products and together with mixed sulfates Ν; · ι ₆ Μ§ (δΟ, |), |, also low melting compounds (melting point about 500 ° C), at the operating temperature of the equipment for the use of energy, they are liquid, cause ash sintering and contaminate the walls of the equipment.

From the above-mentioned publication and from US patent application 2010/0255431, it is also known that vanadium species are particularly aggressive against alkaline metavanadates ΜеVΟ ₃ , where Μе is sodium or potassium. It is also known that vanadium can be converted into compounds such as nickel and magnesium orthovanadates (Μ ₃ (νΟ ₄ ) ₂ ) and magnesium pyrovanadates (Μ§ν ₂ Ο ₇ ), which are chemically and thermally very stable compounds. They are completely inert and not aggressive towards building materials, and in addition they are catalytically inactive in undesirable parallel

- 3 028187 reactions of the transformation type §О ₂ to §О ₃ in an oxidizing medium at temperatures in the range of 250,700 ° С (that is, in the range of heat use of hot flue gases). However, the reactions of the conversion of vanadium to orthovanadates are slow and not quantitative and are inhibited by the presence of iron (for example, Fe ₂ O ₃ during the formation of nickel orthovanadate), undergo competitive interactions (for example Ν α ₂ Ο, Na ₂ 8O ₄ with magnesium orthovanadate give metavanadate) and, in addition, undergo metavanadate) the negative effects of sulfur present (magnesium is preferably converted to sulfate). In particular, the patent application describes the operation of a thermal power unit, including a combustion chamber and a turboexpander, when supplying fuel containing vanadium, sulfur and optionally sodium, in which boron and magnesium are supplied in such an amount that the molar ratio of sodium is 8 = No. ₂ 8 O ₄ / Y ₂ O ₅ , magnesium m = MdO / Y ₂ O ₅ and boron b = B ₂ O ₃ / Y ₂ O ₅ is such that m> 3 + 2L-8 and m <3 + 3L-8 and L is from 0.5 to 3.5, preferably 1 to 3, the combustion products mainly including magnesium orthovanadate, boron and a mixture of magnesium oxide and optionally sodium borate . Thanks to the additive used, corrosion is reduced and the melting temperature of the ash is increased, so that corrosion and the formation of sticky liquid ash are eliminated. With this method, the combustion chamber can operate at higher temperatures than those known from the prior art, for example up to 1140 ° C. In the examples, the temperature in the combustion chamber reaches from 1090 to 1120 ° C. The additives used in this process allow less frequent cleaning of the turbine compared to the additives mentioned in the prior art. It is also important to increase the combustion temperature to 1140 ° C, as a result of which the thermodynamic efficiency of the industrial cycle is increased and the number of stops for cleaning is reduced. It is noted that the mathematical formula for the above quantitative expression of additives may also include the case of negative values of m, when 8 has a higher value. One way or another, it is indicated that the disadvantage of this process is the presence of a large amount of fly ash and the frequency of production shutdowns for cleaning equipment. In accordance with this patent application, it is necessary to work at temperatures not higher than the above, in order to avoid melting of potentially aggressive mixed oxide mixtures and especially their sintering with the formation of thick deposits that are difficult to remove from the equipment, especially from the turbine blades. The abstract of this patent application describes the use of mixed MgOE oxides _of O ₂ , where E is an element 111a, 1Ua, 111b, 1Ub, VL group or a number of lanthanides. The second oxide E _y O ₂ may be selected from the group consisting of B ₂ O _3, A1 ₂ O _3, Fe ₂ O _3, 5> U _2. preferably In ₂ About ₃ , as shown in the examples. With this additive highly melting, loose, refractory and non-sticky ash is formed, which can be easily removed by dry cleaning or washing with water. The ratios to be used between magnesium oxide and the second oxide are indicated in the above equations. The use of these mixed oxides provides effective protection of magnesium from the influence of sulfur (with the formation of sulfate) due to the preferred conversion to mixed borate and eliminates the formation of hazardous sodium metavanadate, in order to increase the melting temperature of ash, as described above, starting from a molar ratio of magnesium / vanadium (MgO / V ₂ O ₅₎ 7 (at a stoichiometric ratio of 3) to a molar ratio of 9 to get maximum increase (1140 ° C) melting / sintering of the fly ash and to avoid corrosion etc. presence of liquid fly ash. It is indicated that although the resulting ash is not very sticky (in contrast to the sticky ash MgO ₄ ) and not melting (not sticky to a temperature of 1140 ° C), however, the drawback of these additives is the fact that in order to transfer vanadium in an inert state, high doses of MDO are used, to which B ₂ O _{3 is} added (the molar ratio of ₂ O ₃ / Y ₂ O ₅ is 3). Therefore, even if the described additive is more advanced in terms of a higher combustion temperature, up to 1140 ° C, and less sticky ash (zeroing of sulfate MD), this however implies high doses of additives (as the sum of MdO and B ₂ O ₃ ) and how the consequence is the presence of significant quantities of fly ash in flue gases with known problems for the technological use of flue gases.

The inefficiencies of the prior art described with respect to additives for vanadium-containing fuels have led to other solutions, such as direct fuel pretreatment, in order to activate processes for eliminating corrosion due to vanadium.

See, for example, I8 patent 2884369, where fractions containing heavy metals and vanadium are treated with activated carbon having a high specific surface in order to remove iron, nickel and vanadium at temperatures up to about 400 ° C. This temperature is specific for the selective removal of contaminating metals and also avoids cracking of heavy oil hydrocarbons.

Another type of pretreatment is disclosed in I8 patent 4116820, which describes the process of removing heavy metals, such as nickel and vanadium, from heavy oil hydrocarbons by pretreatment with oxidized activated carbons at temperatures from 370 to 450 ° C.

Patent I8 6013176 describes a method for removing heavy metals from mineral oil using hydroxides and carbonates of metals of the first and second groups in the presence of a gas containing oxygen and a phase transfer agent at a temperature of from 100 to 180 ° C.

Patent I8 6372124 describes a hydrocarbon purification process using an absorbent consisting of (wt.%) 50-96% alumina and 50-4% calcium oxide and magnesium oxide, where the weight ratio of CaO: MDO is 90:10 to 50:50, the specific surface is more than 100 m ² / g and pre-treatment is carried out at a temperature between 20 and 450 ° C.

Patent FROM 7947167 describes a method for purifying low-grade fuel from vanadium, nickel and other metals by contacting heavy hydrocarbon fractions with an absorbent having a high specific surface area, such as, for example, alumina, alumina hydrate, molybdenum oxide, petroleum coke, activated carbon, zeolites, clays, silicates, inorganic oxides, or combinations thereof.

Patent FROM 5358634 describes a method for removing metals from heavy oil by treating with hydrogen on activated carbon at temperatures from 260 to 649 ° C. and a pressure from 0 to 272 atm.

Patent FROM 7264710 describes a vanadium removal process by treating heavy hydrocarbon fractions under supercritical conditions in the presence of water and an oxidizing agent. The process is carried out at a temperature of 350-600 ° C, carrying out the reforming of the hydrocarbon phase and the oxidation of vanadium, which is removed in the presence of an additive (calcium or iron), with which vanadium forms mixed oxides.

The fuel pretreatments described in the prior art are mainly effective for removing nickel-vanadium from light fractions, but are less effective in the treatment of heavy oil hydrocarbons (asphaltenes, petrolenes) when the C / H ratio increases. These pre-treatments, however, significantly increase the complexity of the entire process of using these fuels and require the use of specialized enterprises.

Thus, there is a need to develop a combustion method that provides direct use of low-quality hydrocarbon fractions and fuel residues containing vanadium in an amount (wt.) Of from 50 to 5000 ppm or higher, at high combustion temperatures, above 1140 ° C, without the above-mentioned disadvantages due to the aggressiveness of vanadium in relation to equipment materials without the use of significant quantities of additives and in any case without the production of flue gases with high concentrations of fly ash, and providing technological use of hot flue gases in energy-consuming devices or equipment for at least 8000 h / year without hazardous emissions of heavy metals into the environment, without significant damage / corrosion to the combustion chamber and building material of the equipment in the event of thermal effects in the production of steam or heat, without significant residual aggressive ash when using pressurized hot flue gases exiting the combustion chamber into turbomachines to obtain nergii, wherein the flue gases is obtained with a low content of fly ash, <10 mg / m ³ of flue gas by dry weight, and minor amounts of incombustible residues TOC concentration <1 ppm by weight, PAHs <10 ^-4 ppm by weight, in the absence of carbon black, the amount of vanadium or its compounds is lower than 1 mg / m ^{3 of} flue gas per dry weight, and at least not determined by X-ray diffraction analysis (XRD) in the form of UaO3, and in the form of U ₂ O ₅ in an amount of <0, 01 mg / m ³ flue gas on a dry mass, where these flue gases are not aggressive with respect to other materials and do not cause a decrease in efficiency due to contamination by sticky deposits of the walls used for heat transfer in the combustion chamber of the equipment.

The applicant unexpectedly found a solution to the aforementioned technical problem; it is a combustion method capable of chemically quantifying vanadium into non-aggressive inert products.

The object of the present invention is a method for the oxy-burning of low-quality gaseous, liquid, solid, optionally fusible hydrocarbon fractions containing vanadium in a weight quantity of 50 to 5000 ppm or higher, to which magnesium is added in the form of oxide, or a water-soluble salt, or in the form of a magnesium compound forming MdO during the combustion process, the combustion chamber is refractory, isothermal or quasi-isothermal, flameless, operating at a temperature of 1250-1450 ° C, under pressure, de oxidizing agent is oxygen, the oxidizing agent is used in a mixture with water or steam, the molar ratio of oxidizing agent: (water / steam) is from about 1: 0.4 to 1: 3, or the oxidizing agent is used in a mixture with recirculating flue or flue gases of energy-using devices, the amount of water / steam is above 30 vol.% by optionally adding water to the recycle flue or flue gases at a molar ratio of oxidizer: (water / steam) in the flue gas as described above; the hydrocarbon fraction is fed in a mixture with water or steam in an amount of water / steam equal to at least 30 wt.%. in relation to the hydrocarbon fraction.

The pressure in the combustion chamber is preferably greater than or equal to from about 102 kPa to about 5000 kPa, preferably greater than or equal to from about 200 to about 3500 kPa.

The oxygen used is pure oxygen or technical oxygen having an oxygen titer above 80% vol. Bringing up to 100% is carried out with inert gases and / or nitrogen.

Technical oxygen is obtained from air by cryogenic distillation, or by selective absorption on zeolites, or by separation on ceramic membranes at high temperature, etc. Technical oxygen is available on the market.

In the process of oxy-combustion, technical oxygen is predominantly used with an oxygen content of 5–18187 sulphide> 98.5 vol.%. Oxygen having a titer of 92-94% U8A (BKA - vacuum short-cycle absorption) and 88-92% UR8A (NVKA - pressure -vacuum short-cycle absorption). Oxygen in the process of the present invention is usually used in excess relative to the stoichiometric amount required for the reaction. In the flue gases, preferably 1 to 3 mol% of unconverted oxygen is present.

The combustion chamber operates in quasi-isothermal conditions, when in all its internal zones the temperature in degrees Celsius changes by no more than ± 5% relative to the main combustion temperature. This means that in practice the combustion chamber has no significant cold zones.

As magnesium compounds forming MDO during the combustion process, both water-soluble salts, for example Mg ₈ O ₄ , and water-insoluble salts are used. The latter are fed into the combustion chamber in the form of aqueous suspensions.

The molar ratio MD: Y, where vanadium means vanadium contained in the fuel, is preferably in the range of 1: 1-2: 1, more preferably from 1.25: 1 to 1.75: 1.

Soot means an organic fuel material in the form of aggregates having a particle size of from 10 nm to about 10 microns, more specifically, oxygen-enriched organic macromolecules based on carbon and hydrogen (partially decomposed hydrocarbon macromolecules due to oxidative reactions) remaining in the exact gases due to incomplete combustion.

Alkali metals (Ma) mean metals of the first group of the periodic system, mainly sodium.

In the case where alkali metals are present in the fuel and the molar ratio Ma: Y is preferably lower than or equal to 1: 3, mixed and inert orthovanadates of Ma, in particular Να and MD, are formed. In the presence of Ma, it is preferable to work with an excess of magnesium close to the upper limit of the above range of MD: U. When the amount of Ma is significantly higher than the aforementioned range of the molar ratios of Ma: Y, it is desirable to pre-treat the fuel, for example by demineralization, to bring the content of these metals to the above limits. These methods are known in the prior art.

When other heavy metals other than vanadium, such as, for example, nickel, iron and cobalt, are present in the feed fuel, they are converted into the corresponding oxides in the combustion chamber of the present invention.

Applicant has unexpectedly discovered that the aforementioned oxides promote the conversion of vanadium compounds to orthovanadates, which are known to be stable and non-aggressive compounds. The amount of these metals present in the fuel is equivalent to the equimolar amount of magnesium commonly used to convert vanadium to orthovanadates.

The amount of water or steam miscible with the fuel is preferably not higher than 80-90% by weight. in relation to the weight of the hydrocarbon fraction. Adding water above this limit can significantly impair the efficiency of heat recovery. Preferably, the combustion chamber operates at temperatures in the range 1300-1400 ° C.

From solid fuels, solid hydrocarbons heated to a molten or liquefied state can be used, which are supplied to the combustion chamber as a viscous liquid.

Solid fuels can also be fed into the combustion chamber after gasification.

Examples of used solid low-quality hydrocarbon fractions are asphaltenes, petrolenes, carbonaceous substances (mainly compounds having a high carbon / hydrogen ratio), petroleum coke, carbonized residues (e.g. POC, partially oxidized hydrocarbons) of petrochemical processes, light cracking bottoms.

Preferably, the addition of magnesium is carried out by supplying an aqueous solution of magnesium sulfate.

The amount of magnesium added depends on the content of vanadium in the fuel. As indicated, the molar ratio MD: Y is in the range from 1: 1 to 2: 1, but can also reach 4: 1. Higher quantities may be used. The upper limit can reach 10: 1 or higher. However, this does not achieve any significant advantage for the combustion process, but increases operating costs.

Isothermal and flameless combustion chambers are known from the prior art, see, for example, patent applications filed by the applicant UO 2005/108867 and UO 2004/094904, incorporated herein by reference.

In the process of the invention, the residence time of the fuel in the combustion chamber is preferably from 0.5 s to 30 minutes, more preferably from 2 to 10 s. If necessary, a longer stay is also possible.

At the base of the combustion chamber is a reservoir for collecting molten ash dripping into it in a liquid state. In the tank, the ash is cooled, for example, by means of a water bath, and is moved in a glassy state to static separators (sedimentation tanks or reservoirs).

According to the invention, when the flue gases obtained in the combustion process are used to generate energy by generating steam or producing heat for other applications, leaving

- 6 028187 the combustion chambers cool the flue gases by mixing them with cold recycle flue gases (after heat recovery) in the mixer in such a ratio of hot flue gases / cold flue gases that the final temperature of the gaseous mixture is approximately 1100 K. The exact temperature obtained in this way is reduced The recirculation of flue gases from energy-using plants is an isoenthalpic process and has no effect on the energy performance of steam, since the technological maximum temperature of superheated steam 8H, acceptable by turbines, is 903 K. Therefore, this does not lead to any negative effect on the cycle of conversion of thermal energy into mechanical / electrical energy through the Rankin cycle and provides a certain advantage, namely that ordinary equipment can be used to extract heat by heat exchange between flue gases and water / steam through a wall constructed of materials traditionally used for those ie the most goals at conventional power plants.

The refractory combustion chamber according to the invention is a conventional combustion chamber, preferably based on alumina, with the addition of approximately 10% chromium and approximately 4% zirconium.

The flue gases corresponding to the pure gas product of combustion can be removed from the circuit by regulating the pressure (for example by throttling) to atmospheric. Conventional post-treatment to remove residual ash and acidity is carried out, for example, by filtration on a cloth bag or bag filter and neutralization by washing with water and alkali (milk of lime). To remove and utilize CO ₂ , if a little water is formed as a result of a chemical reaction, neutralization (washing) under pressure is the preferred solution.

Preferably, a portion of the flue gases corresponding to the pure gaseous product of combustion is diverted downstream of the mixture and expanded for mechanical work, and then sent to a heat recovery unit and atmospheric after-treatment of the flue gases. The expansion can be carried out directly through a turbo expander made of conventional building materials, since the flue gases are essentially free of fly ash and have a temperature of approximately 1100 K.

In an even more preferred embodiment of energy recovery using a turbomachine, a part of the flue gases corresponding to a clean gaseous product of combustion is immediately taken away from the combustion chamber and sent to a conventional turbomachine, and, as a result of appropriate technical modifications of cooling / protecting metal surfaces with a steam layer, it is possible to work with flue gases to a temperature of 1300 ° C with a clear advantage of entering the power plant cycle. In fact, in this way it is possible to combine a Brighton-Joule cycle with a combustion chamber under pressure, for example, 1500 kPa, releasing hot flue gases with a flow rate equal to the net combustion product directly into the turbomachine, with a Rankin cycle that takes heat from the hot recirculating gases. In this method, based on low-quality fuels, the outputs when converting thermal energy into electrical energy can reach above 55%.

The method of the present invention makes it possible to use the aforementioned low quality fuels containing vanadium in highly efficient power plants without significantly affecting the environment. Otherwise, these fuels are practically unsuitable for use in conventional power plants, since they require very complex and expensive equipment and in all cases work with lower outputs.

In the process of the present invention, vanadium is practically quantitatively recovered from low grade hydrocarbon fractions. Vanadium is isolated in the form of orthovanadate and pyrovanadate, among which nickel orthovanadate together with molten ash in the form of vitreous, inert, easily processed balls having a high concentration of useful metals V and Νί is widely used in metallurgy.

The method of the present invention has the following advantages:

acceleration of reactions slowed down according to the prior art to the quantitative conversion of ν ₂ Ο ₅ to orthovanadates / pyrovanadates under gas flow conditions;

segregation of vanadates (both ortho and pyrovanates) and mixed aluminosilicates in the form of molten ash, which accumulates on the refractory walls of the combustion chamber, drips to the base of the combustion chamber and solidifies into slags in the form of glassy balls, useful as concentrates V and Νί in metallurgy;

nickel, which is mainly present in these fuels in a smaller amount relative to vanadium, is converted to nickel orthovanadate, which is a valuable concentrate for separation from vitreous slags;

the absence of a chemical effect on the refractory materials of a combustion chamber based on ordinary alumina or alumina, such as, for example, alumina containing about 10% chromium and about 4% zirconium in the form of highly fired bricks;

a decrease in the content of SО ₃ to insignificant values (approximately below 2 mg / m ^{3 of} flue gases, counting on a dry mass) and the absence of aggressive sulfur condensates on the metal walls of thermal equipment;

combustion is exhaustive, the absence of soot in the flue gases, TOC <1 ppm and PAHs (polyaromatic hydrocarbons, mainly pyrenes) <10 ^-4 mg / m ^{3 of} flue gas per dry weight.

The flue gases leaving the combustion chamber according to the invention directed to the heat utilization section, in addition to being substantially free of soot and having PAHs and TOC within the aforementioned very low limits, show the following analytical characteristics:

the content of fly ash is <100 mg / m ³ , preferably <50 mg / m ^{3 of} flue gas per dry weight, the concentration of magnesium in the flue gases in both oxide and sulfate forms is <1 mg / m ^{3 of} flue gas per dry weight that provides slight corrosion and contamination of the walls of the combustion chamber equipment, the content of vanadium in the form of inert orthovanadate, mainly Νί and MD, in the form of inert pyrovanadates, mainly MD, in amounts expressed as vanadium, is <1 mg / m ^{3 of} flue gas per dry weight; in addition, ν ₂ Ο ₅ (including submicron particles) <0.01 mg / m of flue gas per dry mass,

8О ₃ <2mg / m ³ flue gas on a dry mass,

ΝίΟ <1 mg / m ^{3 of} flue gas per dry weight, X-ray diffraction analysis (XRD) and scanning electron microscope (SEM) analysis of microaggregates show the absence of \ a \ 'O ₃ .

These features of the method of the present invention are confirmed even for very high concentrations of heavy metals (Cr, V, Νί), using fuels containing, for example, up to 5000 ppm weight. vanadium and 2000 ppm weight. nickel, and such difficult-to-process fuels, such as asphaltenes, residual coal ash.

Flue gases with the described characteristics reduce pollution from sticky products on the walls of the combustion chamber equipment to levels that do not affect their efficiency for a time comparable to the performance of conventional industrial equipment (8000 h / g). The absence of pollution is due to both a low content of non-combustible organic residues and a low content of magnesium sulfate.

In addition to the absence of contaminants, in accordance with the process of the present invention, the reactions of the conversion of vanadium to orthovanadates and pyrovanadates and very low residual amounts of 8O ₃ in the flue gases provide a high coefficient of operation. The applicant has established the absence of corrosion processes of building materials (steel, stainless alloys and high-quality stainless alloys) both from vanadium and from sulfuric acid condensate on equipment at the descent of the combustion chamber.

The method of the present invention allows to reduce the release of controlled substances (organic compounds, heavy metals) and to reduce, simplifying them, the processes of post-treatment of flue gases, as indicated above. In practice, only filtration is carried out on a fabric filter with recycle of the filtrate as feed to the installation and neutralization (Ee8O _x ) of the flue gas directed into the chimney.

More specifically, Ee8O _x means a desulfurization system, i.e. equipment for neutralizing sulfur oxides in flue gases.

In the combustion chamber of the present invention takes place:

Xxx - segregation in the molten state of an alkaline salt, in particular sodium salt, with a mixed oxide (compounds, the content of MO ₂ A1 ₂ O ₃ , such as aluminosilicates), absorption and the formation of glassy slag into spherical forms formed by inert vanadates and fuel ash.

The same thing happens when the fuel used contains very high concentrations of alkali metals, as indicated above.

Without going into theory, the applicant believes that under operating conditions in the combustion process according to the present invention, the following reactions take place:

thanks to flameless combustion conditions, some critical parameters (non-linear parameters) are eliminated, which give a chaotic character to the oxidation process in an ordinary flame. This allows you to extend the oxidation process to the entire volume of the combustion chamber in a predefined way, followed by exhaustive oxidation of the fuel without the formation of soot and reduce PAHs to insignificant values;

high and uniform temperature in the combustion chamber promotes the decomposition of alkali metal sulfate and magnesium sulfate to produce the corresponding oxides:

(where M = Ma at x = 2, and M = MD at x = 1) and the decay of 8О ₃ with obtaining 8О ₂ :

Magnesium is completely available in the form of MdO oxide and its amount is sufficient for a quick and exhaustive interaction with U ₂ O ₅ formed as a result of thermal oxidation of vanadium contained in the initial low-quality fuel, for example, in porphyrins, since there are no competitive reactions in which magnesium oxide could participate, since the only competitors, alkali metals, for example sodium, giving harmful and dangerous metavanadates, are excluded from the reaction due to the formation of mixed aluminosilicates. Stable and chemically inert magnesium orthovanadate is formed:

ZMdO + ν ₂ ο ₅ -> Md ₃ U ₂ O ₈ and magnesium pyrovanadate:

2M§0 + ν ₂ Ο ₅ - + Μ§ ₂ ν ₂ Ο ₇ ;

ν ₂ Ο ₅ reacts quantitatively and there is no need to observe a certain stoichiometry of MD-U, since both positive and negative deviations from the stoichiometric amount of orthovanadate are neutralized by the formation of pyrovanadates when the amount of MD is in short supply and by the formation of mixed oxides when the amount of MD is in excess according to the following reaction:

ζΜβΟ + уМ _р О _ч (МДО) ₂ - (М _Р О _Ч ) _У , where М is a metal other than Мd, ζ and у are integers that mix with molten orthovanadates;

nickel present in the form of oxide ΝΐΟ, at the temperature used in the combustion chamber, quickly combines with U ₂ O ₅ to obtain a very stable and inert orthovanadate according to the reaction: 3ΝΪΟ + U ₂ O ₅ Νΐ ₃ ν ₂ Ο ₈ .

This reaction is affected only by the presence of high concentrations of iron oxides in the introduced ash, which are competitive in the formation of vanadates, but do not have any practical effect on the vanadium content in the flue gases removed from the combustion chamber.

In addition, at a preferred temperature range and a sufficient residence time, mainly> 2 s, in the combustion chamber, the formed chemical particles and compounds are melted together with the fireproof ash contained in the fuel (oxide mixture), undergo coalescence and precipitate in the form of droplets on the walls of the combustion chamber a then accumulate quantitatively (> 99% relative to ash balance) at the base of the combustion chamber.

Without going into theory, it can be assumed that in the process according to the present invention, a condition is achieved under which the reagents and products usually subjected to almost uncontrolled, complex, multiple reactions, and the various operating conditions in the present invention are only indicated above and therefore very well controlled in flameless conditions without significant formation of other products downstream of the combustion chamber, since the residual fraction of pollutants and impurities in the exhaust flue gases very low; the following data are given in relation to 1 m ^{3 of} flue gas per dry weight:

fly ash residue <100 mg / m ³ , where:

MD <1 mg / m ³

ZO ₃ <2 mg / m ³ , orthovanadates and pyrovanadates, expressed as V <1 mg / m ³ and U2O5 <0.01 mg / m ³ , X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) of microaggregates show the absence of ash alkaline metavanadates, in particular No. UO3.

In the flue gas exhaust there are practically no chemical products capable of causing undesirable side reactions, such as, for example, U ₂ О ₅ , ЗО ₃ , МдЗО ₄ , and chemical species and products that can regenerate undesirable products downstream of the combustion chamber (lack of mass effect) are inactivated ) even at decreasing temperatures, but during a relatively longer residence time, for example, by reacting magnesium oxide with the formation of sulfate again (sticky ash) and the subsequent reaction of magnesium sulfate magnesium pyrovanadate to form again LP _3.

The applicant believes that in the process of the present invention, in addition to the above said positive effects, the cooling effect on the flue gases of the combustion chamber of cold recirculating flue gases (after heat recovery or recovery) should be taken into account. This represents the first rapid decrease in the temperature of the flue gas to 1100 K (a much lower temperature than the usual temperature known from the prior art), which causes a kinetic suppression of possible subsequent reactions among products formed in the combustion chamber and residual flue gases in the temperature range between 1700 and 1100 K (from the combustion chamber to the apparatus for pre-cooling).

In the temperature range from 1100 to 520 K, mainly for the use of thermal energy, there is a complete conversion of U ₂ O ₅ , which means the absence of U ₂ O ₅ in the flue gases. On the other hand, in the range of 1000–800 K, a complete conversion of GZ ₂ to GO ₃ catalyzed by U ₂ O ₅ could take place, and thus the re-emergence of this chemical product, responsible for destructive sulphurous corrosion in heat-using equipment.

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In this regard, it should be added that the formation of U ₂ O ₅ particles under gas flow conditions can be assumed on an experimental basis (see procedure (1a) in the examples).

Undoubtedly, the chemistry and physical chemistry of vanadium oxides greatly complicate their interactions with other metal oxides that are always present in fuel / processes, especially in the case of flue gases with complex characteristics. However, control experiments were carried out (without interventions). Methodology (1a) shows that vanadium alone at temperatures of 1300-1400 ° C can interact with alumina in a tubular reactor, causing weak staining even at a quantitatively low content. Vanadium predominantly turns into non-wettable particles of U ₂ O ₅ (submicron size), not amenable to filtration on a 0.1 μm filter, which cannot be removed by conventional purification methods, even using acid solutions with high oxidizing ability in ordinary high-performance contact filters (Drexel flasks ) Only using Drexel flasks of very large size with a very high contact surface can a satisfactory percent removal of introduced vanadium be achieved, equal to 70-80%, using working solutions of nitric acid with a pH of 0.5 and adjusted to an oxidation potential of 1.4 eV with hydrogen peroxide.

Typically, in the prior art, the complex interactions of U ₂ O ₅ with other oxides do not allow the U ₂ O ₅ particles and sodium metavanadate to be removed from the plurality of vanadium containing chemicals leaving the combustion chamber. On the contrary, in accordance with the present invention, a quantitative conversion of U ₂ O _{5 is} achieved. The solutions proposed in the prior art are not effective in reducing the effect of vanadium on the equipment materials, which is confirmed by the presence of vanadium downstream of the flue gas even after several complex operations carried out on the descent of combustion / gasification processes, as in the case of a combined cycle gas turbine using syngas from gasification.

On the contrary, in accordance with the process of the present invention, as was indicated, the amount of U2O5 is <0.01 mg / m ^{3 of} flue gases per dry weight, i.e., actually below the sensitivity limit of the analysis method, (see, examples, methods, (1a, 1b and 1c)), in the absence of typical traces of U ₂ O ₅ according to the RSMA (energy dispersive X-ray spectral microanalysis) and SEM. Similarly, sodium metavanadate is not found in accumulated powders collected from the filter.

It was also unexpectedly discovered that when the pressure in the oxy-combustion process is increased to the pressure of the present invention, even without substantially modifying the total amount of residual ash in the flue gases leaving the combustion chamber, the concentration of vanadate, on the contrary, decreases. For example, at the same temperature when working under pressure of 11 bar (relative pressure), the total amount of residual ash decreases slightly compared to that obtained at a pressure of 3 bar, while for vanadium (orthovanadates and pyrovanadates), under the same conditions, a significant decrease is achieved, approximately level 1/3.

In addition to the analytical characteristics, which, as indicated, exclude the presence of undesirable chemical products (MgO, U ₂ O ₅ and NaOU ₃ ) in the flue gases to the sensitivity limit of the analytical method, their absence is confirmed by the study of materials used in equipment and plants after many working cycles, for example 2000 h / g. Inspection of the internal surfaces of the combustion chamber (refractories) and the surfaces of the equipment on the descent shows that no deterioration has occurred. This is further confirmation of the absence of aggressive products, which is proved in turn by the chemical characteristics of the exhaust flue gases. Thus, there is no interaction of residual vanadium with these materials (for example, carbon steel (C8) and stainless steel (ΑΙδΙ 304) in the entire range of operating temperatures, from 750 ° C for ΑΙ8Ι 304, and from 380 ° C for C8 to room temperature .

In addition, the resulting flue gases essentially do not contain aggressive products and compounds directly at the outlet of the combustion chamber, the absence of corrosion phenomena on materials, erosion from powders and surface contaminants allows us to generally establish the norms of flue gases necessary to control the temperature of the combustion chamber under oxy-combustion of low-quality heavy hydrocarbon fractions with high calorific value, with recycle of flue gases collected in the cooling circuit downstream heat generation or utilization, cooling of flue gases leaving the combustion chamber to a temperature (700-800 ° С), compatible with the use of conventional materials in heat recovery or utilization equipment, by direct recycle of flue gases to the cooling circuit at the process operating pressure, not performing operations to clean or remove unwanted products, with maximum thermodynamic efficiency and a minimum increase in operating and fixed or fixed costs.

As already indicated, the method of the present invention allows to process hydrocarbon fractions, characterized by a very variable vanadium content, in a range of values that allow the removal of U ₂ O ₅ and NaaO ₃ from the flue gases downstream of the combustion chamber without corrosion of the equipment on the descent and in the absence of sintering or sticky fly ash, which adheres to the walls of this equipment due to the activation of certain mechanisms (stoichiometric, quantitative 10 028187), which easily adapt to a wide variety of types the logic of vanadium and alkali metal (in particular sodium) contained in fuels. In accordance with the invention, unexpectedly, there has been no deterioration in the efficiency of power equipment, since it is not necessary to clean the surfaces of the equipment on the run for even a long working period, for example, above 8000 h / g.

For amounts of vanadium higher than 5000 ppm, concentrations of vanadium are meant, preferably from about 6000 to 8000 ppm.

The amount of additives used is in the range from 0.5 to 2%. If desired, higher values may be used.

The following are illustrative examples, not limiting the scope of the present invention.

Examples Characteristic Analytical Methods

Characterization of microparticles in flue gases

Microparticles contained in the combustion gases are collected by means of an Andersen impactor (Apdegkep Magk III) equipped with: one preservator (cyclone) capable of removing particles having an aerodynamic diameter greater than 10 μm, sieves for Andersen's impactor for PM 10 microparticles (particles no larger than 10 μm ), operating with a sample flow of 14 l / min, and filters capable of separating fractions having a particle diameter of 10-9 μm, respectively; 9-5.8 microns; 5.8-4.7 microns; 4.7-3.3 microns; 3.3-2.1 microns; 2.1-1.1 microns; 1.1-0.7 microns; 0.7-0.4 microns.

Microparticles with sizes lower than 0.4 μm, which are not stored in the last stage of the Andersen impactor, are filtered on a mica filter for analysis using an atomic force microscope using a pneumatic drive that collects a thermophoretic effect, a sufficient and statistically significant number of particles. The gaseous stream leaving the impactor is then transferred to the condensation system of the steam generated during combustion, where submicron microparticles are collected together with a part of microparticles having a diameter below 10 nm in an amount between 1 and 10 wt.% Of the initial population of particles having nanoscale sizes. The particle fractions after each sample are subjected to physicochemical analysis using scanning electron microscopy (CEM) and X-ray diffraction analysis (XRD). Chemical analysis of individual particles is carried out using an 8EM RNUR § X30 microscope equipped with a thin PCMA system for energy dispersive X-ray spectrometry using an automatic system capable of automatically detecting particles when the detection threshold is exceeded.

Morphological parameters were determined for each of the identified particles by measuring the intensity of the bands typical of the X-ray spectrum and counting them in the corresponding atomic concentrations.

Metal analysis

The analysis was performed using induction plasma spectroscopy using a 1СР (ICP) device (inductively coupled plasma device) and ОЕ§ (OES - optical electronic spectrometer) (Tiego E1ec1goi Sogrogaiop).

For solid phases, compounds were analyzed by X-ray diffraction (X-ray diffraction analysis) combined with ICP.

Chemical potential (eV).

The potential of the solutions was determined using a potentiometer.

Soot analysis

Soot analysis was performed using CEM microscopy. Partially burnt fuel molecules tend to aggregate into clusters (microaggregates) of various sizes and very irregular shapes.

These particles, called cenospheres and plerospheres, are typical representatives of soot (also known as Diesel Particles or Black Carbon) and are clearly identified using a CEM microscope.

Evaluation of the results

Analysis using the Andersen impactor, CEM and PCMA showed the absence of cenospheres and plerospheres. If they are present, then in quantities below the sensitivity limits of these analytical methods. Studies by other analytical methods are shown in example 1.

Other methods used are conventional and are known to those skilled in the art. For example, flue gases from the reactor were detected using a high-speed analytical unit (T95, 1.5 s), specially developed by Ikyeg-Koketoip !, capable of monitoring both large quantities of substances, СО ₂ , and micro quantities of СО, ΝΟ ₂ , § ₂ O ₂ and OOU (total organic carbon, hydrogen flame detector). Analytical blocks analyze gases at a frequency of 10 Hz. The initial signal is recorded, skipping the averaged program data. In parallel, a full gas cycle of the reactor flue gases is monitored, as soon as the gas pressure reaches atmospheric pressure, by a group of PT1K sensors (infrared spectroscopy based on Fourier transform 1128187) that detect Н ₂ О, СО ₂ , ЗО ₂ , СО, N0, ΝΟ ₂ , HC1 with a response time of 40 s.

Example 1

The oil fraction obtained from the heavy oil refining steps and collected from the bottom of the easy cracking unit was charged into a tank equipped with a heating element and a steam heat exchanger. The calorimetric characteristics of the hydrocarbon fraction showed a value of 12 IV (NTS - the lowest calorific value) of 39350 kJ / kg. The material subjected to pyrolysis at a temperature of 605 ° C contained 0.67 wt.%. fireproof ash. Analysis using 1СР-ОЕЗ (ICP-OES optical emission spectrometry with inductively coupled plasma) shows that the ash is mainly formed from alumina and quartz and a small amount of calcium.

Sodium in ash is at a concentration of 1.41 wt.%. Ash also contains heavy metals, among which are the following:

Nickel 42 ppm weight.

Vanadium 287 ppm weight.

Using a gear pump, fuel was fed into a 5M flameless thermal combustion chamber, using oxygen having a titer of 93% vol. At 1650 K and a pressure of 5 bar (600 kPA) as an oxidizing agent and placed in a demonstration unit. The fuel consumption determined using the Coriolis flowmeter was 8.2 kg / min. The introduction into the combustion chamber was carried out by means of a nozzle, using compressed steam to disperse (only dispersion, not atomization) the injected jet. The steam sent to the nozzle head came from a thermal steam generator, had a pressure of 1314 bar and a flow rate of 65 kg / h, while the water added at a speed of 95 kg / h was dispersed through a spray device.

Oxygen having a titer of 99.85% was supplied at a flow rate of 18.2 m ³ / min. Used oxygen came from a cryogenic storage equipped with an evaporator. Oxygen was mixed with compressed air added at a flow rate of 2.4 m ³ / min. The gaseous mixture was introduced into the stream of recirculating flue gases supplied to the combustion chamber in order to control the temperature.

A 0.2 M aqueous solution of magnesium sulfate was injected with a second injection nozzle at a rate of 0.33 L / min.

The demonstration unit was equipped according to the prior art.

The flue gases leaving the combustion chamber were cooled in a pre-cooling apparatus by mixing with recirculating flue gases to a temperature of approximately 1050 K and sent to equipment for heat recovery or use (a steam generator with a superheater ЗН, an EVA evaporator, and final heat-using equipment). On the descent from the equipment for heat utilization and utilization, flue gases having a temperature of approximately 520 K were separated into recirculating flue gases (sent to the combustion chamber and pre-cooling apparatus) by means of a purge pump and into generator flue gases sent to the POT section (subsequent processing flue gas), after reducing the pressure from the pressure in the process to a pressure slightly above atmospheric.

The produced superheated steam ZN (400 ° C, 40 bar) before being sent to the condenser was subjected to quantitative analysis by calibration.

In the MOUTH section, the flue gases were filtered through a cloth bag filter with a powdered vermiculite filter layer, then neutralized with milk of lime (OZO _x ) using a Venturi contact filter and sent to the exhaust chimney.

When passing through the section, heavy metals were sampled using the Andersen impactor (see above) located between the cloth filter and the Venturi contact filter.

The analytical equipment for monitoring emissions from the chimney is a series of analyzers that continuously take samples from the recirculating gases for analysis after dehydration, and consists of

RT1K for determining ZO _X , WITH, except for OOU;

ΝΟΙΚ (non-dispersive infrared gas analyzer) for bulk components;

NRGO (hydrogen flame ionization detector) for continuous analysis of OOU (total organic carbon), and a zirconium oxygen analyzer.

Samples were taken from the flue gases passing through the exhaust chimney to determine the total content of powders and heavy metals (procedures in accordance with European standards).

In the same way, but in batches for 8 hours, flue gas samples were taken to determine dioxins, furans, PCBs (polychlorodiphenyls), and PAHs.

Analytical equipment for sampling batches of flue gases for specific studies of powders (vanadium and, in addition to nickel, magnesium) was located at the following positions or points in the process.

Point 1. Downstream of the combustion chamber, specifically downstream of the pre-cooling apparatus.

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Point 2. Downstream of the fabric filter.

Point 3. Downstream of Oe5O _x (exhaust chimney).

The determination and investigation of powders in flue gases was carried out using the following devices in the following sequence (see methods (1a) and (1b) (see below)): a filter with a quartz thread (particle size 0.1 μm), a capacitor placed in a temperature-controlled bath at 12 ° C, Drexel filled with water (Drexel 1), Drexel filled with acid (Drexel 2), and Drexel, providing a high contact time, filled with an aqueous solution acidified to pH 0.5 with nitric acid, adjusted to the oxidation potential of 1.4 eV by ne hydrogen rexis, and 3 liter Drexel for recovered non-condensable fractions.

The mileage in the combustion process lasts 600 hours (25 days).

At the end, the unit was dismantled at some specific points to collect powder samples, sample core samples of refractory coatings, and extract metal samples (various metals and alloys) for further characteristics.

Point 3.

Among the values analytically determined during the run of flue gases sent to the exhaust chimney, the following are given (values are expressed in mg / m ^{3 of} flue gases per dry weight):

Average value Maximum value

СО 2,3 11

TOC <0.1 0.6.

The following are the average batch sizes of a batch of chimneys (see above) for parachlordibenzodioxin / furan (PCDD / F) and polyaromatic hydrocarbons (PAHs) (8 determinations, 5 of which in the first week) with respect to flue gases per dry weight:

PCDD / F ng 1TE0 / m ³ 0,0003

PAHs μg / m ³ <0.05 (PTX) - 1p1egpiopa1 Tox1C Etshua1ep1 Oiapuu).

For the powders contained in the flue gases, the following average values of the total number of powders were determined, М, Mn and V, respectively, expressed as mg / m ^{3 of} flue gases per dry weight:

Total Powders 1.2

Heavy metals

Νί 0.008

MP 0.002

V <0.001

All other metals having controlled emissions, each <0.001 mg / m ³ .

The consumption of flue gases produced per dry mass, calculated by determining the flow rate and studying the composition, is 940 m ³ / h, including an air flow rate of approximately 50 m ³ / h used to clean analytical instruments and other details.

Studies of a batch of powders at other points in the sampling of the process for characterizing the components (V, Νΐ, Mn) gave the following average results, expressed in mg / m ^{3 of} flue gases per dry weight.

Point 1.

Downstream of the combustion chamber.

Filter

Powders present in the flue gases were collected on a dried and suspended ceramic fiber filter (size 0.1 μm). To take into account the total volume of dried flue gas of 400 l, determined using a volumetric counter, the amount of dry powder was multiplied by a factor of 1 / 0.4 = 2.5 to obtain the corresponding value, expressed as mg / m ^{3 of} flue gas to dry weight :

Total powders 88.

Capacitor

In the condenser, water present in the gaseous products of combustion condenses at a dew point of 18 ° C. 263 ml of condensate were collected with a dried flue gas volume of 400 l. The amount of each heavy metal found in the condensate was multiplied by a factor of 0.236 / 0.4 = 0.6575, obtaining the corresponding amount, expressed as mg / m ^{3 of} flue gas per dry weight:

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Νί 0.91

MD 0.002

V 0.02 (the solution has a pH of 1.1).

The contents of Drexel 1 + Drexel 2.

In each of the two Drexels, the amount of solution was 30 ml. These solutions were combined and the amount of each heavy metal, expressed as mg / m ^{3 of} flue gas by dry weight, was calculated by multiplying the found analytical value by a coefficient of 0.06 / 0.4 = 0.15. The following values were obtained:

Νί 0.02

M £ 0.03

V <0.001.

Drexel 3.

The volume of the solution in Drexel 3 was 60 ml. Carrying out calculations as well as for the content of each heavy metal in Drexel 1 + Dresel 2, the following amounts of heavy metals were found:

Νί <0.001

Mg <0.001

V <0.001.

Part of the solid residue collected on the filter was deposited, the collected fractions were combined and the following studies were performed: determination of the absolute composition using ICP-OES, determination of the phase composition using SAR and SEM visualization of microaggregates.

When X-ray analysis, ν ₂ Ο ₅ or No. UO ₃ were not detected in any phase. SEM analysis showed the absence of bands typical of ν ₂ Ο ₅ . The concentration of ZO ₃ determined for single samples of recirculating flue gases ranged from 0.5 to 1.5 mg / m ^{3 of} flue gas per dry weight. The amount of vitreous slag removed from the sumps and collected in the bath for 600 h was a little less than 2 tons. Analysis of samples taken from different bags of cloth filter showed that they contain different amounts of aluminosilicates. The percentage of vanadium was on average 4 wt.% And nickel 0.5 wt.%.

An inspection of the dismantled parts of the equipment performed at the end of the work period showed the absence of any sticky powders and an insignificant amount of deposits in non-working dead zones. The data of the ESZ (DCS - Distributed Control System) of process parameters, indicating the efficiency of heat transfer, showed that during the period of operation the efficiency remains almost constant, which coincides with previous observations.

The collected powders were analyzed by XRD and SEM. Neither ν ₂ Ο ₅ nor No. UO ₃ were detected.

Specific characteristics ν ₂ Ο _{5 of} example 1 performed in a flowing gas reactor procedure (1a)

A gas stream of CO ₂ and O ₂ in a molar ratio of 90:10 at a rate of 6.3 l / min is fed into a tubular reactor with a diameter of 50 mm made of high purity alumina and thermostatically controlled in a heating apparatus at 1400 ° C.

An aerosol of 0.1 M aqueous solution of vanadium (νθδΟ ₄ solution, vanadyl sulfate) with a flow rate of 20 ml / h for 8 hours is injected through a Venturi feeder.

The gases leaving the tube reactor are cooled with a metal finger cooled by water (immersion cooling thermostat), fed to a glass fiber filter with a particle size of 0.1 μm, and then introduced into a flask (condenser) placed in a bath thermostatically controlled at 18 ° C, where excess moisture condenses . A battery of three vessels of the Drexel type is sequentially connected to the outlet of the condenser using a tube, i.e., Drexel 1, Drexel 2, Drexel 3 are sequentially. In each vessel (Drexel) gas is bubbled through a stable aqueous phase so that the liquid / gas contact occurs with the greatest efficiency. The first vessel attached to the condenser (Drexel 1) contained 30 ml of demineralized water, the second (Drexel 2) contained 60 ml of water, acidified to pH 0.5 with nitric acid, the third and last (Drexel 3) contained 300 ml of acidified nitric acid to pH 0.5 of water with an oxidation potential of 1.4 eV adjusted with hydrogen peroxide. After 8 hours, the aerosol supply was stopped and the reactor was kept under a weak stream of dry air at a temperature of 1300 ° C for 16 hours.

The operation was repeated three times, a total of 0.048 gM vanadium was added, equal to approximately 2.5 g vanadium.

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At the end of the test, the tubular reactor was dismantled and disassembled into fragments. X-ray diffraction analysis of these fragments showed that the quantitative penetration of Y ₂ About ₅ . into the walls of the reactor is not significant (ICP).

The condenser was also dismantled and the inner surface of the flask, after removing the condensate from the base of the flask, was cleaned with a spatula and then washed with an aqueous acid solution. Then, the washing solution was combined with the condensed liquid phase. The final volume of the condensed liquid phase was 430 cm ³ . This phase was analyzed using ICP. Similarly, the solution from Drexel 1 was also subjected to ICP analysis. The concentration of vanadium in the analyzed samples was <0.01 μg / L.

The liquid phase contained in Drexel 2 was also analyzed using ICP. The concentration of vanadium was <0.01 μg / L.

It should be noted that the summation of the contents of Drexel 1 and Drexel 2 does not have any effect on the mass balance of vanadium, since the concentration of vanadium is below the analytical sensitivity limit.

In Drexel 3, the concentration of vanadium was 1.6 mg / L, equal to the collected amount of vanadium 0.016 gM. Multiplying the amount in g / l by the volume of the solution (0.3 l), we find that the amount of vanadium in Drexel is 0.48 g, which is approximately 20% of the vanadium added.

The second part of the methodology (1a).

The operations were carried out under the same conditions as in the first part, but with the following modifications: taking into account the flow rate of a solution of vanadium and transport gas, a volume of solution was provided in Drexel 3

450 cm ³ due to a more effective degree of dispersion and a longer contact time so that, at very high efficiency, the concentration of released vanadium was 1.98 g / l.

The mass balance was> 70%, which shows the corpuscular nature of ν ₂ Ο ₅ generated in the reaction gas stream. The specific characteristics of ν ₂ Ο _{5 of} example 1, performed in a flowing gas reactor - method (1b)

A gas stream of CO2 and O2 is supplied to a pipe reactor of the same type as in procedure (1a) in a molar ratio of 90:10 at a rate of 6.3 l / min and analytically pure §O ₂ with a flow rate of 0.01 l / min

An aerosol of an aqueous solution obtained by mixing is injected through a Venturi feeder by mixing: 0.1 M νθδθ ₄ (vanadyl sulfate), 0.125 M MgO ₄ (water soluble magnesium sulfate) to have a molar ratio of vanadium: magnesium 1: 1, 25 at a flow rate of 20 ml / h. The experiment lasts 8 hours.

The gases leaving the tube reactor are cooled as described in procedure (1a), then fed to a glass fiber filter with a particle size of 0.1 μm and sequentially into the same equipment as described in method (1a), part two, with respect to highly efficient drexels.

The operation is repeated under the same conditions and time of the process as described in procedure (1a), with a full supply of 0.048 gM vanadium (approximately 2.5 g).

At the end of the test, the tubular reactor was dismantled and disassembled into fragments. The surfaces of the fragments forming the inner wall of the tubular reactor, which during the test were in contact with a vanadyl sulfate aerosol, had a darker, more thickened appearance upon visual inspection, especially in the outer part leaving the pipe reactor. However, XRD analysis of these fragments did not show vanadium penetration. X-ray diffraction analysis of the dark surface layer showed the presence of only magnesium orthovanadate and pyrovanadate.

The solid filter residue was analyzed by X-ray diffraction in combination with ICP analysis. The weight of the collected solid residue was 47 mg. After dissolving in an aqueous medium, ICP analysis showed that the amount of vanadium in the collected residue was 15.6 mg.

Then the capacitor was dismantled, the inner surface was thoroughly washed with an aqueous acid solution, which was then weighed and combined with the condensate collected at the base of the condenser. The volume of the resulting solution was 425 cm ³ .

ICP analysis showed that magnesium and vanadium are present in the molar ratios Мд / ν between the stoichiometry of magnesium orthovanadate and magnesium pyrovanadate. The amount of vanadium in the collected fraction was 0.9 mg.

The liquid phase contained in Drexel 1 was subjected to ICP analysis in a similar manner. The concentration of vanadium, measured using ICP analysis, was below the sensitivity of the analytical limit (<0.01 μg / L).

The same results were obtained for the liquid phases from Drexel 2 and Drexel 3, respectively.

The final mass balance for vanadium was 96%, given the deposits on the alumina of the tubular reactor and on the cooling finger.

Example 2 (comparative).

The same 5 M \ U1 demonstration unit was used under the same conditions as in Example 1, but Vipkeg-S heavy oil fuel containing 41 ppm of vanadium was used as fuel. Fuel was supplied at a rate of 7.8 kg / min.

Burning was carried out without the introduction of additives (MdO) at a travel time of 120 hours

In the end, after cooling and disassembling parts of the equipment, ash was collected that accumulated on the walls of the heat recovery steam generator and on the bends of the flue gas pipeline.

ICP-OES analysis of this ash showed that the amount of vanadium is 2.6 wt.%.

X-ray diffraction also identified ν ₂ Ο ₅ and Νανθ ₃ in the ash, and typical bands ν ₂ Ο _{5 in the} SEM.

At the base of the economizer (ECO) (heater), iron sulfates were present on the surfaces of the heat exchange tubes. The surface of products from alloyed materials (ΑΙδΙ 304Н) has deteriorated due to the formation of nickel on the surface of vanadates (nickel derivatives of alloyed materials).

Claims (10)

CLAIM 1. A method of burning fuel in the presence of an oxidizing agent, where the starting fuel is low-quality gaseous, liquid, solid, as well as hard-melting hydrocarbon fractions containing vanadium in a weight amount of 50 to 500 ppm or higher, in which the hydrocarbon fraction is fed in a mixture with water or steam into the combustion chamber with an amount of water / steam of at least 30 wt.% with respect to the hydrocarbon fraction; while the following additives are fed into the chamber: magnesium in the form of an oxide or in the form of a magnesium compound forming MDO during combustion; wherein the combustion chamber is refractory, isothermal or quasi-isothermal, flameless, operating at a temperature of 1250-1450 ° C under pressure so that additives and a mixture of the hydrocarbon fraction with water or steam in this combustion chamber are burned in the presence of an oxidizing agent, where the oxidizing agent is oxygen, having the oxygen titer is above 80 vol.%, and bringing it to 100% is carried out with inert gases and / or nitrogen, the oxidizing agent being used in a mixture with water or steam at an oxidizing: water / steam molar ratio of approximately but from 1: 0.4 to 1: 3, or the oxidizing agent is used in a mixture with recirculating flue or flue gases coming from energy-using devices, while the amount of water / steam in these recirculating flue or flue gases coming from energy-using devices , support above 30 vol.% by adding to them, if necessary, water, and the molar ratio of the oxidizing agent: (water / steam contained in these recycle gases) is the same as described above. 2. The method according to claim 1, where the pressure in the combustion chamber is greater than or equal to from 102 to 5000 kPa. 3. The method according to claims 1 to 2, where the pressure in the combustion chamber is higher or equal to from 200 to 3500 kPa. 4. The method according to claims 1 to 3, where the oxidizing agent is pure oxygen or technical oxygen having a titer above 80 vol.%. 5. The method according to claims 1 to 4, where the molar ratio MD ^ is in the range 1: 1-2: 1. 6. The method according to claim 5, where the molar ratio MD ^ is in the range from 1.25: 1 to 1.75: 1. 7. The method according to claims 1-6, where the temperature in the combustion chamber is from 1300 to 1400 ° C. 8. The method according to claims 1 to 7, where the solid hydrocarbon fractions are selected from asphaltenes, petrolenes, carbonaceous substances, petroleum coke, carbonized residues of petrochemical processes, heavy residues of oil refineries. 9. The method according to claims 1 to 8, where the addition of magnesium is carried out by introducing an aqueous solution of magnesium sulfate. 10. The method according to claims 1 to 9, where the residence time of the fuel in the combustion chamber is from 0.5 s to 30 minutes